In the bowl of a heavy-duty mixer, beat the butter with the flat paddle attachment on the medium speed until creamy. Add the sugar gradually and continue beating until light and fluffy, about 5 minutes. In another bowl, stir together the flour, cocoa, espresso powder and salt. Add to the creamed mixture and beat on low speed until incorporated. Scrape the soft dough onto a large piece of plastic wrap and gather together into a ball. Refrigerate for 1 to 2 hours, or until firm enough to roll out. You may chill it overnight; just let it soften a bit at room temperature before proceeding. Preheat oven to 325 degrees. Line 2 sheet pans with parchment paper. Roll out the dough on a lightly floured surface to 1/2-inch thickness. Cut out cookies with a cookie cutter of your choice. These baking instructions are for 3-inch cookies. If you make small cookies, reduce the baking time, larger cookies will require a longer baking time. Reroll any extra dough and cut out as many cookies as possible. Transfer the cookies to the prepared pans, keeping them at least 1-inch apart. Bake for 20 to 25 minutes, rotating the pans front to back halfway through the baking time. These cookies are so dark that it is impossible to see if they are beginning to color. Use the time suggested and check to see if the edges and bottoms are completely dry. You should be able to lift a cookie up with a spatula to peek at the bottom; the cookie should be baked enough to remain stiff and not break. Set the pans directly on a wire rack to cool for 5 minutes. Then remove the cookies to the rack and cool completely. The sheet pans must be cooled completely between uses, but you will probably be able to reuse the parchment. The cookies are best eaten within 1 week; store them at room temperature in an airtight container.
Recipe courtesy of Dede Wilson, Author Bake It to the Limit